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Figure 2 Summary of Functional Findings

Intact immunoglobulin (Ig)G of dilated cardiomyopathy (DCM) patients induced negative inotropic effects by binding via their Fab part to the antigenic epitope on cardiomyocytes and then via their Fc part to the Fc receptor IIa (FcR) (A). The F(ab')₂ fragments of these antibodies inhibited the effect of intact DCM IgG (B), as did Fc fragments of normal IgG (C). Reconstitution of Fc parts by sequential incubation of cardiomyocytes with DCM F(ab')₂ fragments and goat-anti-human F(ab') IgG induced a negative inotropic effect (D) comparable to findings for intact DCM IgG. A detailed description of Fc receptor cross linking is in the Discussion section. AG = antigen.